The Lymphoma-Leukemia Program is a unified multidisciplinary study of malignant lymphomas and related leukemias and immunoproliferative disorders that has as its goal the definition of their cellular and clinical characteristics in terms of modern understanding of immunology, including the T and B lymphocytic systems and alterations of lymphocyte transformation. It combines a multiparameter approach employing a variety of immunologic surface marker technics with cytochemistry, ultrastructural, in vitro and immunoglobulin detecting technics for the cellular definition and with in-depth Hodgkin's staging technics for the defining of clinical expressions. The results of the initial definitional phase during the first two years have demonstrated the effectiveness of this multiparameter definitional approach in characterizing human lymphoid neoplasms according to the T and B cell systems and relating these neoplasms to abnormalities of lymphocyte transformation and to the functional lymphoma classification of Lukes and Collins. A Southern California Lymphoma Group involving 28 major area hospitals also has been developed, as part of the regional collaboration to enhance the collection of fresh lymphoma case material for study. It also extends to the community the morphologic, technical and clinical expertise that influences the quality of patient care. This program interrelates with regional epidemiologic and cancer control programs. In the renewal phase of the program the definitional phase will be continued as a basis for in depth areas of investigation that have evolved out of the initial phase. These involve the following areas: IV. Control Mechanisms in Lymphoma Induction and Progression; V. Membrane and Cytoplasmic Immunoperoxidase; VI. Exploratory Data Analysis; VII. Animal Models; VIII. Cell Surface Receptors and Antigens; IX. Cell Kinetics; X. Cytogenetics; XI. Role of Stromal Cells; XII. HLA and B Cell Typing; XIII. Epidemiology.